On the Detectability of Density Distributions of Asteroids and SAGD Reservoirs Using Gravimetry and MUON Tomography
Density Distribution , Asteroids , Itokawa , Gravimetry , Muon Tomography , SAGD reservoir
In this thesis, the procedures of modelling density distributions for different targets are investigated. In the process of evaluating density distributions of asteroids, gravity forward modelling shows that homogeneous and heterogeneous distributions are distinguishable. Also, this study demonstrates that muon tomography forward and inversion modelling of SAGD reservoirs could be used for monitoring fluid migration and bitumen depletion in the subsurface. Two different asteroids and spherical models with homogeneous and heterogeneous density distributions are investigated and the resulting surface gravitational accelerations are calculated. The asteroid forward modelling assists in the analysis of surface gravimetry sensitivity, by studying the heterogeneity of asteroids and surface boulder detectability. Results indicate that asteroids with heterogeneous and homogeneous density distributions are distinguishable. However, a gravimeter with sub-mGal accuracy is needed to sense asteroid surface gravity. Results show that a boulder of 8 m3 causes gravitational accelerations on the order of µGal and is not detectable using gravimetry with sub-mGal accuracy. A real SAGD density model is used at two time steps and forward modelled using muon tomography. This results in maps of opacity and muon count in a 2D plane view of the reservoir. The forward modelled 2D image arrays, used to construct the 2D reservoir plane view at surface, estimate bitumen depletion around wellbores during the raising phase and the spreading phase. The depletion patterns in the reservoir are studied by testing different arrays of muon sensors in the in-line and cross-line directions. Results show that depletion trends can be resolved with high resolution by using 120 sensors and also when using 60 sensors with a reduced resolution. In the inversion modeling approach, 3D density change models are estimated using 2D opacity image arrays as observations. The depletion trends around wellbores are determined individually until the reservoir reaches the spreading phase when depletion areas become interconnected.